A research of the epidemiology of enterohaemorragic E.coli O157 in wild rodents

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To survey the epidemiology of enterohaemorragic Escherichia coli, (E.coli) wild rodents, river water and soils were collected. Verotoxin producing E.coli were isolated from 3 of 211 wild rodents (1.4%) captured in a mountainous area and 1 of 62 (1.6%) in the place of relating domestic animals. Serotype O157 E.coli, which was typical enterohaemorragic E.coli (EHEC) serotype, was isolated form wild rodents, but it was decided as non-pathogenic E.coli. Four pathogenic isolates were identified the production of Vero toxin 1 (VT1) by the toxin detection kit and PCR, but it could not be done in O-serotype. And, I examine an effective method to isolate EHEC from a sample of soil and river water, but it was not possible to isolate EHEC from these environment factors. While EHEC were experimentally inoculated into some kinds of soils and examined the existence period in these soils at different temperature. Extinction of EHEC was early in a condition of 37℃ and it became hardly to detect the organisms at 3 months after inoculation. But, at 23℃ the number of bacteria is kept the considerable amounts in soils. However a high number was maintained in the soil during approximately 1 month independently of temperature condition. It was suggested that the feces from EHEC infecting cattle fall to the ground, the ground soil is polluted by EHEC and that pollution will be continued between several months. Furthermore, I examined to detect the Vero toxin antibody at 252 serum samples from wild rodents. Three samples were reacted to VT 1 only and 4 samples were reacted to VT1 and VT2. But there is no sample to react to VT2 only. Total at 7 samples (2.8%) the antibody to Vero toxin was detected. And, 5 samples (2.0%) showed O-agglutination to O157 at the serum dilution 80 times. In this study, EHEC O 157 : H7 was not isolated from wild rodents, but it suggested that there is high possibility of possession of EHEC O157 at wild rodents.